Navigate to your Ultimate Doom folder. (wherever you installed Steam/steamapps/common/ultimate doom/base) There should be three .conf files in there. dosbox.conf, which you don't care about, ultimatem.conf, used for the "modern" mouse controls, and ultimate.conf used for the classic controls. They're plain text files so open them in notepad, find the output=surface token, change it to output=ddraw, and save.

While you're in there, also set aspect=true to fix the aspect ratio (so the game is properly stretched to a 4:3 resolution, as it would've been on any monitor back in the day) and you'll likely need to increase the sensitivity. I use 200 on a system with mouse acceleration disabled.

You shouldn't need to do change the output for any of the other Doom games since they're already set to use ddraw. The sensitivity is set way too high for my mouse in the other games, so you might end up having to tweak that at least.

Hi guys, tried the above but it made the screen very small and in the top left hand side of the screen - I have no idea what I'm doing but willing to experiment. After changing several things I tried fullresolution=1920*1200 on both files mentioned above - now it plays full screen. guess if you change it to your max monitor resolution it'll work...

Tried the ddraw solution but I'm still having trouble with the graphics glitching after one minute. Does anyone have any other solutions I might be able to try?Quick Edit: So far it seems to be happening whenever I'm in the pause menu. I'm running a Windows 7 64 bit laptop if that helps.